Recently, due to stringent government regulations and the safety hazards associated with the use of organic solvents in coating systems for dosage forms, emphasis has shifted from solvent-based to water-based coating formulations. New polymeric dispersions have been developed and intensive research is being conducted to maximize the use of water dispersible colloidal particles. However, these aqueous formulations have generally exhibited shortcomings during the coating process.
One major problem is the tackiness which occurs during the curing of polymeric coatings. Although elevated temperatures are required to drive off water rapidly and deposit a film on the product, usually moderate temperatures (30.degree.-50.degree.) are employed in order to avoid the tackiness that has been frequently observed. Once the product is coated, the deposited film requires treatment at lower temperatures for extended periods of time to fully coalesce the polymer beads and ensure a continuous film. If elevated temperatures are employed, coalescence time may be shortened and reproducible release profiles achieved. However, the film usually becomes tacky and makes product handling difficult.